水华生消过程中沉积物微生物变化及其对重金属赋存形态的影响

Although great efforts have been done in past years, algal blooms are still serious in Chinese lakes presently. Moreover, increasing industrial pollution causes greater difficulty in lake treatment in recent years. So it is necessary to explore new methods to treat environment of lake. Microbes in sediment not only produce great impact on biogeochemical cycle of element but also affect environmental behavior of pollutant, so they are significant to improve environment of lake. Unfortunately, although there are many reports related to sediment microbes in previous studies, less attention is paid to microbial shift in sediment during algal blooms of lake, and much less attention is paid to effect of microbial shift on environmental behavior of pollutant. This increases difficulty in deeply evaluating effect of algal bloom on ecosystem of lake, and improving environment of lake by microbes in sediment. In this study, microbial shift and their effects on heavy metal speciation during outbreak and extinction of algal blooms will be investigated in Chaohu Lake through field in-situ experiment and simulation experiment respectively. Advanced molecular biological methods are used to indicate change of microbial community structure, microbial biomass with special function, biological enzyme activity in sediment. In addition, relationship between microbial shift and heavy metal speciation during outbreak and decline of algal blooms is also discussed. This study will provide evidence for deeply evaluating effect of algal bloom on ecosystem of lake, and improving environment of lake by microbes in sediment.

虽然经过多年治理，但我国湖泊水华现象依然严重，加上近年湖泊工业污染增加，湖泊环境治理仍面临巨大压力。沉积物微生物既是元素生物地球化学循环的主要参与者，又是污染物环境行为的主要影响者，对改善湖泊环境有重要作用和价值。虽然之前开展了很多沉积物微生物方面的研究，但却很少关注水华生成和消亡过程对沉积物微生物的影响，更少涉及沉积物微生物变化对污染物环境行为的影响，这不但有碍于深入评价水华对湖泊生态系统的影响，而且也不利于利用沉积物微生物改善湖泊环境。本研究拟以浅水湖泊巢湖为对象，通过野外原位实验和室内微宇宙模拟实验，结合现代分子生物技术分析水华生消过程中沉积物微生物的变化及其对重金属赋存形态的影响，将重点关注水华生成和消亡过程中沉积物微生物群落结构、特殊功能微生物、生物酶等的变化以及它们与重金属赋存形态变化的关系，为深入评价水华对湖泊生态系统的影响、利用沉积物微生物改善湖泊环境等提供科学依据。

本研究以巢湖为对象，于2012年5月15日～9月19日在水华区和非水华区进行了8次水体和沉积物样品采集，分析水华生消过程对水体理化性质、沉积物生物酶活性、特殊功能微生物生物量和微生物群落结构的影响，以及沉积物微生物变化对重金属赋存形态的影响。主要结论如下：.（1）巢湖水华形成期为5月中旬至6月中旬，持续期为6月中旬至9月上旬，之后进入消亡期。水体透明度、pH和溶解氧在水华区和非水华区大部分时间存在显著差异，且随水华生消过程呈不同的变化趋势。非水华区水体和沉积物中各形态氮磷浓度明显低于水华区，且随时间变化幅度相对较小。在水华区，水体氮磷浓度在水华形成期和水华持续前期呈下降趋势，但在水华持续后期和消亡期呈增加趋势。.（2）水华生消过程对沉积物生物酶活性的影响与酶的种类有关。除部分时段的碱性磷酸酶外，水华区沉积物脲酶、过氧化氢酶、多酚氧化酶活性均高于非水华区。2种水解酶活性主要受沉积物pH值和底物含量影响，而2种氧化还原酶活性受沉积物TOC含量影响显著。.（3）PCR-DGGE分析表明，非水华区沉积物微生物的种类、Shannon-Wiener指数、Simpson指数随时间变化较小，微生物相似度较高，温度可能是影响非水华区微生物群落结构波动的主要因子；在水华区，沉积物微生物的种类、Shannon-Wiener指数在水华形成期和消亡期较低，在水华持续期较高，而Simpson指数则呈相反趋势，微生物相似度相对较低，温度和水华导致的水体性质变化可能是沉积物微生物变化的主要影响因子。.（4）水华区特殊功能微生物生物量均显著高于非水华区，且随水华生消过程变化非常明显，总体呈先增后减的变化趋势；非水华区沉积物微生物生物量随时间变化幅度较小。上述变化可能与水华引起的沉积物理化性质（如DO、pH、TOC等）的变化密切相关。.（5）残渣态是水华生消过程中沉积物Cr、Pb、Cu、Ni和Fe存在的主要形态，Mn和Cd主要以可溶态和可还原态存在。除了可还原态的Fe和可氧化态的Cu，水华生消过程对其他不同形态重金属含量的影响均较小。